Magnetic compensator



Oct. 8, 1963 J. F. CHANDLER ETAL 3,106,653

MAGNETIC COMPENSATOR Filed June 8. 1956 2 Sheets-Sheet 1 JAMES F CHANDLER RAYMOND C. FIGLEWICZ JOHN LRENNICK uvmvroxs.

THEIR ATTORNEY.

MAGNETIC COMPENSATOR 2 Sheets-Sheet 2 Filed June 8. 1956 FlG.4

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3,166,658 MAGNETIC COMPENSATOR James F. Chandler and Raymond C. Figlewicz, Chicago, and .lolm L. Rennick, Elmwood Park, Ill., assignors to Zenith Radio Corporation, a corporation of Delaware Filed June 8, 1956, Ser. No. 590,163 17 (Ilaims. (Cl. 3l377) This invention relates to a magnetic compensator for use with color cathode-ray tubes. More particularly the invention has to do with a device for improving the color registration in such tubes.

in present day image reproducers utilized in color television receivers, electrons projected from one or more electron guns are projected through a deflection system toward a color screen assembly. The screen assembly is spaced from the deflection system by an intermediate tube portion usually referred to as the cone, although this portion may have an actual shape other than that of a true cone. The color screen usually is comprised of many thousands of minute areas or dots of luminescent material; the luminescent areas are arranged in a discrete pattern usually consisting of groups, referred to a color triads, each including three different phosphors respectively capable of producing three different colors of light under electron bombardment. Other types of screen assemblies have been suggested or demonstrated; one well known form has the different color producing phosphors sequentially arranged in a series of strips across the face of the color tube.

In order to accurately direct electrons from an electron gun to phosphors of a selected color-type at any given instant, present day color tubes include what has been termed a color-selection barrier which is spaced a short distance ahead of the color screen in the path of electron travel. One such color-selection barrier, adapted to cooperate with a screen of the type having dots of phosphor material arranged in triads, comprises a thin metal plate provided with a plurality of minute apertures of a number approximating the number of color triads on the screen and arranged within the tube to have a particular geometric configuration with respect to the position of the color triads and the source of electrons. In one type of color tube, the color-selection barrier is so aligned that it physically blocks electrons traveling along path-s other than those desired. In another type of color tube, the apertures in the color-selection barrier are made somewhat larger than the width of the desired electron paths, but the barrier in cooperation with other electrodes serves'to focusclectrons passing through the apertures and causes the electrons to travel only along desired paths. Thus, the color-selection barrier is utilized for the purpose of insuring that projected electrons are guided so as to bombard only desired portions of the color screen. If, at a particular instant, it is desired to cause a beam of electrons to strike a red-producing phosphor dot on the color screen, the barrier cooperates with the screen and source of electrons either to focus the electrons onto that dot or to eliminate any electrons other than those traveling along a path directly toward the dot.

One of the major problems in the manufacture and use of color tubes is the attainment and maintenance of accurate alignment of the various components of the tube so as to insure satisfactory color registration. A tube has perfect color registration when particular electrons impinging upon the screen at a particular instant strike only phosphors that produce the color intended to be produced by those electrons at that instant; that is, if it is intended to produce only the color red, then the electron beam intended to cause red reproduction must be so directed as to strike only red-producing phosphors.

As a practical matter, however, very few color tubes are produced which inherently have such perfect color registration that there is no need for some type of additional compensation; in the commercial production of color tubes, it has been found that one of the leading causes of the rejection of finished tubes has been unsatisfactory color registration.

Various methods have been suggested for providing compensation for the inherent inaccuracies of the color tubes to improve the registration between the impinging electrons and the luminescent areas of the screen. One aid to the solution of the problem has. been the use of the so-called purifier? the purifier is a device for establishing a magnetic held across the neck portion of the color tube, between the usual deflection yoke and the cathode. By adjusting the purifier to vary the intensity and direction of the magnetic field cutting across the neck, an improvement in color registration is obtained; the field alters the direction of travel of the electrons for the purpose of bringing them into correct alignment with respect to the color-selection barrier and the color screen. While this type of compensation has proved beneficial, it has certain inherent disadvantages as well. Its action and effect is actually to defocus the electron beam or beams traveling through the electron gun, whereas the electron gun provides most efiicient and satisfactory operation when the electrons travel along a certain fixed path. A corollary problem which arises with the use of purifier magnets placed on the neck has been the production of what is well known as neck shadow. Neck shadow results when the beam is decentered to such an extent that it actually strikes the tube envelope in the neck; as a result, certain areas of the screen do not receive electrons and consequently are blacked out.

Another frequent problem with commercial color tubes arises from what has been called edge impurity. With this difficulty, the color registration may be adequate over the central portion of the screen but very poor around the outer edge portions. This difficulty is due in part to the shape of the screen surface with respect to the source of electrons and in part to stray magnetic and electric fields. The conventional screen surface does not lie in a sphere having its center at the effectual source of the deflected electron beams and, as a consequence, it is necessary to provide compensation to the deflected beam in order to vary its point of convergence as the beam is deflected to scan the screen surface. As a practical matter, present day commercial color tubes and their associated convergence compensation apparatus rarely are capable of perfect registration over the entire scanned area of the color screen, and, in addition, the elimination of all stray fields is practically impossible. The net result is that it is highly improbable that any particular commercially produced color tube will have perfect alignment, or even uniform misalignment, over its entire screen surface, especially near its outer portions. One suggestion has been made to utilize magnets placed around the outer edge of the screen surface to establish magnetic fields in the immediate vicinity of the screen and adjustable to vary the magnetic field strength in the vicinity of different portions of the screen; these magnets have usually been mounted just outside the color tube envelope at the rim of the screen surface. Their effect is to provide somewhat independent control over the direction of electron travel immediately before the electrons impinge upon the screen. One of the disadvantages of this type of correction device is that it effectually increases the width of the color tube structure and thereby increases the dimensions of the enclosing cabinet. This type of correction assembly also has been found to be expensive to manufacture and diflicult of adjustment.

Furthermore, in order to obtain satisfactory color registration, it usually has been necessary to employ some type of compensation, as described above for example, both at the neck portion and around the rim of the screen of the color tube. In performing the necessary adjustment to the individual magnets of these assemblies, it is necessary to have access to both ends of the color tube at the same time, since adjustment of the compensation at one end affects the compensation needed at the other end; special cabinet provisions must be provided to permit easy access to the area surrounding the rim of the color screen.

It is accordingly a general object of the present invention to provide a new and improved magnetic compensator.

It is also an object of the present invention to provide an improved magnetic compensator for obtaining accurate color registration, a compensator which is easy to adjust, which is economical to produce, and which is capable of being manufactured from parts of simple construction and assembly.

It is another object of the present invention to provide an improved magnetic compensator which is adapted to be mounted on a color tube in a position where it does not increase the size of cabinet space necessary to contain the color tube and associated receiver chassis and where it is readily accessible for servicing.

It is a further object of the present invention to provide a magnetic compensator for improving color registration while avoiding defocusing of the electron beam during its passage through the electron gun.

A still further object of the present invention is to provide an improved magnetic compensator for obtaining satisfactory color registration in color cathode-ray tubes which, without the employment of the compensator, would be rejected as having unsatisfactory color registration.

Still another object of the present invention is to provide a device for improving color registration in a color cathode-ray tube, which is effective to control electron travel across the entire area encompassed by the cone of the color tube, and which at the same time is effective to provide localized control over localized portions of the region within the cone.

It is another aim of the present invention to provide a device capable of establishing a magnetic field of completely controllable intensity and configuration within the region encompassed by the cone of a color tube between its deflection system and its color-selection barrrer.

It is a further aim of the present invention to provide an improved magnetic compensator adapted to mount around the cone portion of a color cathode-ray tube and which achieves the same results heretofore accomplished by utilizing two different magnetic compensators disposed near opposite ends of the color tube.

In accordance with the invention, improved color registration is obtained by means of a ferromagnetic yoke structure adapted to encircle a color tube between its deflection system and its color-selection barrier. A plurality of magnets are supported at spaced points around the periphery of the yoke structure so as to be in magnetic coupling relation therewith, and means are provided to independently adjust each magnet with respect to each of a pair of co-ordinate axes, that is, each of the magnets, or the fields therefrom, are independently adjustable with two degrees of freedom. The resultant magnetic field encompassed by the yoke structure, in the space defined by the cathode-ray tube cone, is controllable in both intensity and configuration. By simple, selective adjustment of each magnet, correct color registration is readily obtainable.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is a perspective view, partially broken away, showing a magnetic compensator constructed in accordance with the invention and mounted upon a color cathode-ray tube;

FIGURE 2 is a fragmentary view showing one of a plurality of magnets mounted on the magnetic compensator;

FIGURE 3 is a perspective view of an alternative form of the magnetic compensator;

FIGURE 4 is a cross-sectional view taken along lines 4-4 in FIGURE 1 and indicating one mode of adjustment of the magnetic compensator;

FIGURE 5 is a view similar to FIGURE 4 but indicating a different condition of adjustment;

FIGURE 6 is a fragmentary view taken along line 6-6 in FIGURE 1 and indicating another mode of adjustment; and

FIGURE 7 is a view similar to FIGURE 6 but indicating a different condition of adjustment.

In FIGURE 1, there is shown a color cathode-ray tube It having a deflection yoke 11 mounted upon its neck 12, both of which may be of conventional construction. Within neck 12, there preferably are three electron guns (not shown) for projecting electrons out of neck portion 12 through the deflection system, including yoke 11, and toward a color screen 13 afiixed across the large end of a cone portion 14 which terminates at its smaller end in neck portion 12. The electron guns may be of conventional construction and cooperate with the usual convergence compensator disposed on neck portion 12 behind yoke 11 (out of sight in FIGURE 1). Mounted substantially parallel with screen 13 and one the side thereof toward neck 12 is a color-selection barrier 15. Tube 10 is of the type employing a large number of color triads on screen 13; color-selection barrier 15 is provided with a correspondingly large number of minute apertures having a predetermined geometrical disposition with respect to the position of the triads and the position of the three electron guns, one for each color, mounted within neck 12.

The design, construction, and operation of such color tubes is now well known and voluminous taXtu-al material is available on this subject. There is, therefore, no need to enter into detailed considerations of color tube 10 by itself; it will sulfice to say that, when placed into use in a suitable color receiver, electrons projected out of neck portion 112 are deflected by yoke 11 so as to describe a zig-zag path progressing downwardly across screen 13 and to successively traverse different portions of the screen. With respect to each of the electron guns in the presently embodied type of color tubes, the apertures in color-selection barrier 15 are aligned with discrete areas of color producing phosphor on screen 13 so as to only permit the passage of electrons from a particular gun that will impinge upon a predetermined selected discrete phosphor portion of screen 13. The design of color tubes is very critical, particularly with respect to the necessary alignment between the apertures in color-selection barrier 15, the discrete phosphor areas on screen 13, and the electron gun or guns. Electrons traveling through color tube 10- are also subject to the influence of stray magnetic and electrostatic fields.

The invention contemplates a simple magnetic device, indicated at 20 in FIGURE 1, which is effective to compensate for irregularities in the registration between impinging electrons and discrete phosphor areas of screen 13 intended to be struck by the electrons at any given instant. Device 20 herein includes four ferromagnetic strips 21 spaced end to end circumferentially around cone 14 between color-selection barrier 15 and yoke 11, preferably nearer the latter than to the former. Positioned at the air gap 22 defined by the adjacent, outwardly bent ends of each adjacent pair of strips 21 is one of four magnets 23 each supported to permit individual rotational displacement of the magnetic field patterns thereof with two degrees of freedom; that is, each magnet is adjustable with respect to each of a pair of co-ordinate axes. As shown, strips 21 are aflixed to a band 25 of non-magnetic material, such as aluminum, encircling cone 14 and which preferably is an extension of a support frame 11a for yoke ill. Magnets 23 are in the form of a ring and are polarized along a diameter. of the ring to form a principal magnetic axisor polarization direction of the ring as indicat d by arrow A in FIGURE 2. Each magnet is supported from band 25 by an L-shaped bracket 26 swivelably afiixed to band 25 by means of a friction mounting 27 comprising a bolt secured through one leg of bracket 26 and band 25 by a nut and resilient washer. Each magnet 23 is swivelably mounted to the other leg of bracket 26 by means of a friction mounting 28 comprising a bolt secured through the bracket and through the bore of the magnet by a nut and resilient washer. Thus, the assembly comprising each magnet and the associated bracket 26 may be twisted about one axis 2% for which mounting 27 forms a pivot, while either separately or concurrently, each magnet 23 may be rotated about its principal axis 28a for which mounting 28 defines a pivot.

It will thus be seen that yoke structure 20 includes a substantially continuous ring of ferromagnetic material comprising a plurality of strips 21. Upon yoke 20 are mounted a plurality of magnets supported one each at each of air gaps 22. Each magnet has a predetermined polarization direction A which can be independently adjusted about either of two co-ordinate axes; each mag net thus has two degrees of freedom. As shown, axes 27a and 28a both intercept the magnet, permitting maximum freedom in a minimum of space. In another embodiment of the present invention, as illustrated in FIG- URE 3, a yoke 26a of ferromagnetic material is formed in one piece 21a of generally uniform cross section but with areas 22a of reduced cross section spaced around the ring to provide relatively high reluctances such as are present at air gaps 22 of FIGURE 1; the below described operation refers to this embodiment as well as to that of FIGURE 1. Alternatively, a continuous ring of generally uniform cross sectional area may be employed together with magnets 23 having a field strength of sufficient intensity to saturate the portion of the ring immediately adjacent the magnets which, in an equivalent manner, establishes the existence of a region of high reluctance in place of the illustrated air gaps 22 or the reduced areas 22a.

The operation of magnetic compensator 26) (or 251a) may best be explained by reference to FIGURES 4 through 7. In FIGURE 4, the four magnets 23 are oriented in a manner to produce, by interlinking of their individual fluxes in the yoke, flux cutting across the region, indicated at 31, encompassed by yoke structure Zil; thus, when yoke 20 is mounted on tube it the flux cuts across the space within cone 14 from top to bottom as indicated by dash lines at 30. The two magnets on the right side of FIGURE 4 are positioned with their polarization directions A angularly adjusted to induce flux into strips 21 in a counter-clockwise circumferential direction. At the same time, the two magnets on the left side of yoke 2t? are oriented to induce flux into strips 21 in a clockwise direction. These fluxes meet in the one of the ferromagnetic strips 21 running across the top of cone 14 with the result that the combined flux is directed downwardly toward the bottom one of strips 21; when magnets 23 are oriented to induce the greatest amount of flux into strips 21, their polarization paths A lie in the plane of yoke 2t? and the field pattern within region 31 is fairly uniform.

In FIGURE 5, magnets 23 still are oriented with their polarization directions A lying in the plane of yoke 20, but they have been readjusted to effect a net field pattern cutting across region 31 in a horizontal direction from left to right. This is achieved by orienting the upper two of magnets 23 in a direction to induce fiux into strips 21 in a counter-clockwise direction, while orienting the lower two of magnets 23 to induce clockwise flux into stripsZl. Similarly, it is evident that merely by reorienting magnets 23, the direction of the magnet field cutting through region 31, and hence thru the space within cone 14, may be rotated to any position; merely by varying the amount of angular adjustment of each of the polarization directions A about the respective axes 28a (FIGURE 2), a greater or lesser amount of field rotation is effected than is shown in making the adjustment to change the field pattern from that of FIGURE 4 to that of FIGURE 5. Forexample, when the magnets in the upper-right and lower-left corners of FIGURE 5 are rotated to orient their polarization directions A radially into or out of cone 14, there two magnets induce substantially no flux into strips 21. With the other two magnets, in the upper-left and lower-right corners, positioned as shown in FIGURE 5, the net flux cuts across the space Within cone M from the lower-left corner to the upperright corner. It will be apparent that full 360-degree rotation of the generally planar net field cutting across the space within cone 14 is readily obtainable. Although the flux 30 in FIGURES 4 and 5 is shown as having substantial uniformity, the correction required for a particular color tube may require non-uniformity of the net flux pattern across cone 14. Such non-uniformity is readily obtained simply by de-orienting one, or more, of magnets 23 to reduce the amount of flux coupled into the adjacent strips 21 by the de-oriented magnet.

As so far described, only one degree of freedom of rotation of the individual magnetic fields from magnets 23 has been exercised. FIGURES 6 and 7 illustrate adjustments of the magnetic field in 'a second degree of freedom. In FIGURE 6, magnets 23 are oriented to lie in the plane of yoke 20 the same as in FIGURES 4 and 5. When adjusted in this manner, magnets 23 tend to induce their flux into strips 21' as described above. However, as shown in FIGURE 7, when magnets 23 are swiveled about axis 27a (FIGURE 2), at least some of the individual flux from each magnet is induced directly into region 31 as indicated by flux lines 33. When magnets 23 are disposed with their polarization directions at right angles to the plane of yoke 21, a substantial portion of the individual flux from each magnet passes directly into region 31. Of course, the simple magnets shown and adjusted as in FIGURE 7 have a total individual free space field pattern including flux lines describing loops outside of region 31 as indicated at 34; the principal feature to be noted is that the major axis of the field illustrated in FIGURE 7 is at right angles to the plane of yoke 21, and, hence, flux 33 is created directly Within region 31 individually from each magnet. It is evident that magnets 23 may be adjusted to position their polarization directions, and, hence, their individual field patterns, at an angle intersecting the plane of yoke 20 and somewhere between the positions shown in FIGURES 6 and 7, so that a portion of the individual magnet flux is induced into strips 21, while another portion of the flux passes directly through region 31. With respect to flux 33 induced directly into region 31 by magnets 23, each individual magnet has itsngreatest affect on the portion of region 31 in the vicinity of that magnet; that is, swiveling of the magnet in the upper righthand corner of FIGURE 4 about its axis 27a will have the greatest effect in the upper righthand portion of region 31. Thus, each magnet is capable of creating a localized magnetic field havring a predominant effect on a respective portionof region 31, while the magnets together are capable of adjustment to induce flux into strips 21 and hence establish a mag netic field of variable intensity and direction cutting across region 31.

It has been seen that each of magnets 23 is adjustable with two degrees of freedom; rotation of each magnet about its axis 27a controls the amount of flux created directly within localized portions of region 31, while rotation of each magnet about its axis 28a controls the flux cutting across region 31 from strips 21. Hence, the resultant magnetic field within region 31 may be adjusted to have virtually any desired intensity and configuration. This wide range of control of the resultant field pattern permits variation of the intensity and direction of the field cutting across the space within cone 14 thereby accomplishing what has heretofore usually been done with a purifier magnet assembly located on neck 12. At the same time, the localized corrective fields from each individual magnet may be easily adjusted to make the necessary corrections in local areas of region 31 as is usually accomplished by means of bulky magnet assemblies surrounding the rim of screen 13. As shown, complete control of the color registration within color tube is accomplished, during operation of the latter, with just four magnets each of a very standard variety and all mounted on a single, unitary device. The mounting for the magnets is of simple construction and assembly as is the preferred supporting frame 25 which is part of the same frame 11a utilized to support yoke 11. Strips 21 may be simply and economically formed of standard sheet iron.

It will be apparent that adjustment of each magnet in one of its degrees of freedom will at the same time have an effect on its field pattern corresponding with its other degree of freedom. Thus, in adjusting the system as applied to a particular operating color tube, it is usually necessary to retouch one or more of the other magnets each time .0116 of the magnets is adjusted. However, it has been found that, starting with a random positioning of the magnets, a technician can bring all of the magnets into their correct position and thus achieve uniform and accurate color registration in a matter of a minute or so.

While a particular embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Accordingly, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We claim:

1. A system for improving color registration in a color cathode-ray tube in which electrons are projected through a defiection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a ferromagnetic yoke structure encircling said color tube and disposed solely between said deflection device and said color-selection barrier; a plurality of magnets, each having a predetermined polarization direction, supported at spaced points around said yoke structure in magnetic coupling relation therewith; and means permitting adjustment of the polarization direction of each magnet with respect to each of a pair of angularly displaced axes independently for establishing a resultant magnetic field of controllable intensity and configuration within the region encompassed by said yoke structure.

2. A system for improving color registration in a color cathode-ray tube in which electrons are projected through a deflection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a yoke structure, including a discontinuous ring of ferromagnetic material having air gaps at spaced points around the periphery of said ring, encircling said color tube and disposed solely between said deflection device and said color-selection barrier; a plurality of magnets, each having a predetermined polarization direction, supported one each at each of said air gaps in magnetic coup-ling relation with said ring; and means permitting adjustment of b the polarization direction of each magnet with respect to each of a pair of angularly displaced axes independently for establishing a resultant magnetic field of controllable intensity and configuration within the region eucompassed by said yoke structure.

3. A system for improving color registration in a color cathode-ray tube in which electrons are projected through a deflection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a yoke structure, comprising a continuous ferromagnetic ring of generally uniform cross-sectional area but having portions at spaced points around its periphery of reduced cross-sectional area, encircling said color tube and disposed solely between said deflection device and said colorselection barrier; a plurality of magnets, each having a predetermined polarization direction, supported one each at each of said spaced points in magnetic coupling relation with said ring; and means permitting adjustment of the polarization direction of each magnet with respect to each of a pair of angularly displaced axes independently for establishing a resultant magnetic field of controllable intensity and configuration within the region encompassed by said yoke structure.

4. A system for improving color registration in a color cathode-ray tube in which electrons are projected through a deflection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a ferromagnetic yoke structure encircling said color tube between said deflection device and said color-selection barrier; a plurality of magnets, each having a predetermined free space field pattern, supported at spaced points around said yoke structure in magnetic coupling relation therewith; and means permitting independent adjustment of the field pattern of each magnet in at least two degrees of rotational freedom for establishing, by interlinking in said yoke structure said individual field patterns and by emanation of flux directly from each of said magnets, a resultant magnetic field of controllable intensity and configuration within the region encompassed by said yoke structure.

5. A system for improving color registration in a color cathode-ray tube in which electrons are projected through a deflection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a ferromagnetic yoke structure supported between said deflection device and said color-selection barrier in encircling relation with the cone of said color tube; a plurality of magnets individually magnetically coupled to said yoke at spaced points around the periphery thereof; and means to independently rotate each magnet about each of a pair of angularly displaced axes for establishing, by interlinking in said yoke structure the flux emanating individually from said magnets and by emanation of flux directly from each of said magnets, a resultant magnetic field of controllable intensity and configuration in the space within said cone.

6. A system for improving color registration in a color cathode-ray tube having a screen assembly, including a color-selection barrier, spaced from an electron-deflection device by a cone portion, said system comprising: four strips of ferromagnetic material disposed end to end circumferentially around said cone portion, each of said strips substantially spanning a quadrant of said cone portion and said strips defining spaces between the adjacent ends of each adjacent pair of said strips; four magnets, each having a predetermined polarization direction, supported one each at each of said spaces; and means permitting independent rotational adjustment of the polarization direction of each magnet about each of a pair of co-ordinate axes for establishing a resultant magnetic field of controllable intensity and configuration within the region encompassed by said cone portion.

7. A system for improving color registration in a color cathode-ray tube in which electrons are projected along a predetermined axis through a deflection device to a luminescent screen assembly including a color-selection barrier, said system comprising: a ferromagnetic yoke structure encircling said color tube between said deflection device and color-selection barrier; a plurality of magnets each having a predetermined polarization direction; and respective support means, individually angularly -ad justable with respect to each of a pair of angularly displaced axes, for mounting said magnets at spaced points around said yoke structure in magnetic coupling relation therewith to permit independent angular adjustment of the polarization direction of each magnet with respect to said yoke structure and with respect to said predetermined axis to establish, by interlinking in said yoke structure the flux emanating individually from said magnets and by emanation of flux directly from each of said magnets, a resultant magnetic field of controllable intensity and configuration within the region encompassed by said yoke structure.

8. A compensation apparatus for use with 'a color cathode-ray tube in which electrons are projected through a deflection system to a luminescent screen assembly including a color-selection barrier, said apparatus comprising: a substantially continuous yoke of ferromagnetic material adapted to encircle the cone of said color tube between said color-selection barrier and said deflection system; a plurality of magnets individually magnetically coupled to said yoke at spaced points around the periphery thereof; and means for varying the intensity of flux induced circumferentially into said yoke from each magnet independently and for establishing localized magnetic fields, adjustable independently of the net amount of said circumferentially induced flux, within predetermined portions of the region encompassed by said yoke structure to create a resultant magnetic field within said region of controllable intensity and configuration.

9. A magnetic compensating device comprising: means including a ferromagnetic yoke structure and a plurality of magnets coupled magnetically to said yoke structure at spaced points around the periphery thereof for establishing a generally planar magnetic field across the region encompassed by said yoke structure; and means for rotating said magnetic field within its plane and for concurrently establishing localized magnetic fields, individually intersecting said plane and adjustable in magnitude and direction independently of the magnitude and direction of said first-mentioned magnetic field, Within predetermined different portions of said region to create a resultant magnetic field of controllable intensity and configuration within said region.

10. A magnetic compensating device comprising: means including a discontinuous ring of ferromagnetic material having air gaps at space-d points around the periphery of said ring; means including a plurality of magnets magnetically coupled to said ring, one each at each of said air gaps, for establishing a generally planar magnetic field in the region encompassed by said ring; and means for rotating said magnetic field within its plane and for concurrently establishing localized magnetic fields, individually intersecting said plane and adjustable in magnitude and direction independently of the magnitude and direction of said first-mentioned magnetic field, within predetermined diilerent portions of said region to create a resultant magnetic field of controllable intensity and configuration within said region.

11. A magnetic compensating device comprising: means including a ferromagnetic yoke structure and a plurality of magnets coupled magnetically to said yoke structure at spaced points around the periphery thereof for establishing a generally planar magnetic field across the region encompassed by said yoke structure; and means permitting independent adjustment of each magnet in at least two degrees of rotational freedom for establishing a resultant magnetic field of controllable intensity and configuration within said region.

12. A magnetic compensating device comprising: a ferromagnetic yoke structure; a plurality of magnets, each t It) having a predetermined free space field pattern, supported at spaced points around said yoke structure in magnetic coupling relation therewith; and means permitting independent adjustment of the field pattern of each magnet in at least two degrees of rotational freedom for establishing a resultant magnetic field of controllable intensity and configuration within the region encompassed by said yoke structure. A

13. A magetic compensating device comprising: a ferromagnetic yoke structure; a plurality of magnets, each having a predetermined polarization direction, supported at spaced points around said yoke "structure in magnetic coupling relation therewith; and means permitting independent rotational adjustment of the polarization direction of each magnet with respect to each of a pair of co-or'dinate axes to vary the intensity and direction of magnetic flux coupled from each magnet into said yoke structure and to vary the intensity and direction of magnetic flux passing directly into the region encompassed by said yoke for establishing a result-ant magnetic field of controllable intensity and configuration within said region.

14. A magnetic compensating device comprising: a ferromagnetic yoke structure; a plurality of magnets, each having a predetermined polarization direction, supported at spaced points around said yoke structure in magnetic coupling relationship therewith; and means permitting independent rotation of the polarization direction of each magnet with respect to each of a pair of co-ordinate axes both intercepting that magnet for varying the intensity and direction of magnetic flux coupled from each magnet into said yoke structure and for varying the intensity and direction of magnetic flux passing directly into the region encompassed by said yoke for establishing a resultant field of controllable intensity and configuration within said region.

15. A compensating device for use with a color cathoderay tube in which electrons are projected through a deflection device to a luminescent screen assembly including a color-selection barrier, said compensating device comprising: a ferromagnetic yoke structure encircling said color tube between said deflection device and said color-selection barrier; and means, including a plurality of magnets individually birotationally adjustably supported at spaced points around said yoke structure and magnetically coupled therewith, for establishing within the region encompassed by said yoke snucture a resultant magnetic field having independently adjustable components parallel and perpendicular to said luminescent screen assembly, whereby substantially uniform color registration throughout the entire luminescent screen may be achieved by adjustment of said magnets.

16. A system for improving color-registration in a color cathode-ray tube in which electrodes are projected generally along the longitudinal axis of said tube through a deflection device to a luminescent screen assembly including a color selection barrier, said system comprising: a ferromagnetic yoke structure supported between said deflection device and said color selection barrier in encircling relation with the cone of said color tube; means including a plurality of magnets individually magnetically coupled to said yoke at spaced points around the periphery thereof for establishing, by interlinking in said yoke structure the flux emanating individual-1y from said magnets, a magnetic field across the space Withinsaid cone; and means for varying the coupling between said magnets and said yoke structure to rotate said magnetic field about said longitudinal axis and for establishing localized additional magnetic fields, adjustable independently of said first-mentioned magnetic field, about said longitudinal axis and penetrating different portions of said space by direct emanation of flux from said magnets, thereby creating a resultant magnetic field of controllable intensity and configuration within said space.

17. In combination, a cathode-ray tube having an axis, a plurality of electron guns spaced from each other and operable to produce ray beams initially directed parallel to said axis, a shadow mask in a plane normal to the axis and having a plurality of openings capable of passing electrons, and a phosphor plate disposed to receive electrons passing through said openings and having discrete colored light producing phosphor areas, a set of such phosphor areas being disposed in alignment with each of said openings to produce illumination of color determined by the electron gun from which the electrons come; means to sweep said ray beams in unison over the face of the shadow mask to produce a television image in color; and means operable to produce a magnetic field crosswise of the tube between said last means and the shadow mask, said means being capable of producing a 1?. generally linear magnetic field crosswise of the tube of adjustable orientation and intensity and being capable of an adjustable degree of distortion from the substantially linear configuration.

References Cited in the file of this patent UNITED STATES PATENTS 2,498,354 Bocciare-lli Feb. 21, 1950 2,513,221 Webb June 27, 1950 2,541,446 Trott Feb. 13, 1951 2,591,159 Kabuss Apr. 1, 1952 2,743,389 Giuffrida Apr. 24, 1956 2,766,393 Casey Oct. 9,1956 2,816,244 Hillegass Dec. 10, 1957 2,825,835 He-ppner Mar. 4, 1958 

2. A SYSTEM FOR IMPROVING COLOR REGISTRATION IN A COLOR CATHODE-RAY TUBE IN WHICH ELETRONS ARE PROJECTED THROUGH A DEFLECTION DEVICE TO A LUMINESCENT SCREEN ASSEMBLY INCLUDING A COLOR-SELECTION BARRIER, SAID SYSTEM COMPRISING: A YOKE STRUCTURE, INCLUDING A DISCONTINUOUS RING OF FERROMAGNETIC MATERIAL HAVING AIR GAPS AT SPACED POINTS AROUND THE PERIPHERY OF SAID RING, ENCIRCLING SAID COLOR TUBE AND DISPOSED SOLELY BETWEEN SAID DEFLECTION DEVICE AND SAID COLOR-SELECTION BARRIER; A PLURALITY OF MAGNETS, EACH HAVING A PREDETERMINED POLARIZATION DIRECTION, SUPPORTED ONE EACH AT EACH OF SAID AIR GAPS IN MAGNETIC COUPLING RELATION WITH SAID RING; AND MEANS PERMITTING ADJUSTMENT OF THE POLARIZATION DIRECTION OF EACH MAGNET WITH RESPECT TO EACH OF A PAIR OF ANGULARLY DISPLACED AXES INDEPENDENTLY FOR ESTABLISHING A RESULTANT MAGNETIC FIELD OF CONTROLLABLE INTENSITY AND CONFIGURATION WITHIN THE REGION ENCOMPASSED BY SAID YOKE STRUCTURE. 